Studies on certain aspects of flavin/flavoprotein biosynthesis, function, and control will be continued. Ongoing investigations with flavokinase, riboflavin binding proteins, and pyridoxamine (pyridoxine) 5'-phosphate oxidase will receive particular attention in the near future, since the pure systems and considerable basic information are now in hand. The molecular properties of hepatic flavokinase will be delineated by physico-chemical techniques. Eventually, comparison of the properties of the enzymes from different sources, especially mammalian tissues, will be done. Specific properties and differences among riboflavin-binding proteins will be investigated. More complete characterization of the hepatic form should help indicate how it is altered for release to circulation. Chemical modification of essential amino acid residues within hepatic pyridoxine (pyridoxamine) 5'-phosphate oxidase will be completed for Arg/Lys, and kinetic studies will begin to interface with the static measurements. Further aspects on change in level and control will be done using intact animals of different age, sex, strain, and nutritional (flavin) status.